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Duchenne and Becker muscular dystrophy

Reviewed February 2012

What is Duchenne and Becker muscular dystrophy?

Muscular dystrophies are a group of genetic conditions characterized by progressive muscle weakness and wasting (atrophy). The Duchenne and Becker types of muscular dystrophy are two related conditions that primarily affect skeletal muscles, which are used for movement, and heart (cardiac) muscle. These forms of muscular dystrophy occur almost exclusively in males.

Duchenne and Becker muscular dystrophies have similar signs and symptoms and are caused by different mutations in the same gene. The two conditions differ in their severity, age of onset, and rate of progression. In boys with Duchenne muscular dystrophy, muscle weakness tends to appear in early childhood and worsen rapidly. Affected children may have delayed motor skills, such as sitting, standing, and walking. They are usually wheelchair-dependent by adolescence. The signs and symptoms of Becker muscular dystrophy are usually milder and more varied. In most cases, muscle weakness becomes apparent later in childhood or in adolescence and worsens at a much slower rate.

Both the Duchenne and Becker forms of muscular dystrophy are associated with a heart condition called cardiomyopathy. This form of heart disease weakens the cardiac muscle, preventing the heart from pumping blood efficiently. In both Duchenne and Becker muscular dystrophy, cardiomyopathy typically begins in adolescence. Later, the heart muscle becomes enlarged, and the heart problems develop into a condition known as dilated cardiomyopathy. Signs and symptoms of dilated cardiomyopathy can include an irregular heartbeat (arrhythmia), shortness of breath, extreme tiredness (fatigue), and swelling of the legs and feet. These heart problems worsen rapidly and become life-threatening in many cases. Males with Duchenne muscular dystrophy typically live into their twenties, while males with Becker muscular dystrophy can survive into their forties or beyond.

How common is Duchenne and Becker muscular dystrophy?

Duchenne and Becker muscular dystrophies together affect 1 in 3,500 to 5,000 newborn males worldwide. Between 400 and 600 boys in the United States are born with these conditions each year.

What genes are related to Duchenne and Becker muscular dystrophy?

Mutations in the DMD gene cause the Duchenne and Becker forms of muscular dystrophy. The DMD gene provides instructions for making a protein called dystrophin. This protein is located primarily in skeletal and cardiac muscle, where it helps stabilize and protect muscle fibers. Dystrophin may also play a role in chemical signaling within cells.

Mutations in the DMD gene alter the structure or function of dystrophin or prevent any functional dystrophin from being produced. Muscle cells without enough of this protein become damaged as muscles repeatedly contract and relax with use. The damaged fibers weaken and die over time, leading to the muscle weakness and heart problems characteristic of Duchenne and Becker muscular dystrophies. Mutations that lead to an abnormal version of dystrophin that retains some function usually cause Becker muscular dystrophy, while mutations that prevent the production of any functional dystrophin tend to cause Duchenne muscular dystrophy.

Because Duchenne and Becker muscular dystrophies result from faulty or missing dystrophin, these conditions are classified as dystrophinopathies.

Related Gene(s)

Changes in this gene are associated with Duchenne and Becker muscular dystrophy.

DMD

How do people inherit Duchenne and Becker muscular dystrophy?

This condition is inherited in an X-linked recessive pattern. The gene associated with this condition is located on the X chromosome, which is one of the two sex chromosomes. In males (who have only one X chromosome), one altered copy of the gene in each cell is sufficient to cause the condition. In females (who have two X chromosomes), a mutation would have to occur in both copies of the gene to cause the disorder. Because it is unlikely that females will have two altered copies of this gene, males are affected by X-linked recessive disorders much more frequently than females. A characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons.

In about two-thirds of cases, an affected male inherits the mutation from his mother, who carries one altered copy of the DMD gene. The other one-third of cases probably result from new mutations in the gene in affected males and are not inherited.

In X-linked recessive inheritance, a female with one mutated copy of the gene in each cell is called a carrier. She can pass on the altered gene but usually does not experience signs and symptoms of the disorder. Occasionally, however, females who carry a DMD gene mutation may have muscle weakness and cramping. These symptoms are typically milder than the severe muscle weakness and atrophy seen in affected males. Females who carry a DMD gene mutation also have an increased risk of developing heart abnormalities including cardiomyopathy.

Where can I find information about diagnosis or management of Duchenne and Becker muscular dystrophy?

These resources address the diagnosis or management of Duchenne and Becker muscular dystrophy and may include treatment providers.

You might also find information on the diagnosis or management of Duchenne and Becker muscular dystrophy in
Educational resources (http://ghr.nlm.nih.gov/condition/duchenne-and-becker-muscular-dystrophy/show/Educational+resources) and Patient support (http://ghr.nlm.nih.gov/condition/duchenne-and-becker-muscular-dystrophy/show/Patient+support).

General information about the diagnosis (http://ghr.nlm.nih.gov/handbook/consult/diagnosis) and management (http://ghr.nlm.nih.gov/handbook/consult/treatment) of genetic conditions is available in the Handbook.
Read more about genetic testing (http://ghr.nlm.nih.gov/handbook/testing), particularly the difference between clinical tests and research tests (http://ghr.nlm.nih.gov/handbook/testing/researchtesting).

To locate a healthcare provider, see How can I find a genetics professional in my area? (http://ghr.nlm.nih.gov/handbook/consult/findingprofessional) in the Handbook.

Where can I find additional information about Duchenne and Becker muscular dystrophy?

You may find the following resources about Duchenne and Becker muscular dystrophy helpful. These materials are written for the general public.

Merck Manual of Medical Information, Second Home Edition (http://www.merckmanuals.com/home/childrens_health_issues/muscular_dystrophies_and_related_disorders/duchenne_and_becker_muscular_dystrophies.html)

OMIM - Genetic disorder catalog

What other names do people use for Duchenne and Becker muscular dystrophy?

DBMD

Duchenne/Becker muscular dystrophy

muscular dystrophy, Duchenne and Becker types

muscular dystrophy, pseudohypertrophic

For more information about naming genetic conditions, see the Genetics Home Reference
Condition Naming Guidelines (http://ghr.nlm.nih.gov/ConditionNameGuide)
and
How are genetic conditions and genes named? (http://ghr.nlm.nih.gov/handbook/mutationsanddisorders/naming) in the Handbook.

What if I still have specific questions about Duchenne and Becker muscular dystrophy?

The resources on this site should not be used as a substitute for
professional medical care or advice. Users seeking information about
a personal genetic disease, syndrome, or condition should consult with a qualified
healthcare professional.
See How can I find a genetics professional in my area? (http://ghr.nlm.nih.gov/handbook/consult/findingprofessional) in the Handbook.